1. Field of the Invention
The invention relates to a feed pump having a driven impeller which rotates in a pump housing and has a plurality of rings of vane chambers which are arranged at an end face of the impeller and concentrically enclose one another, feed channels arranged opposite the rings of the vane chambers in a wall of the pump housing, and guide vanes which define the vane chambers relative to the impeller and which are arranged so as to be inclined by an angle with respect to the axis of rotation of the impeller.
2. Description of the Related Art
Feed pumps having impellers with plural rings of vane chambers are often used for feeding fuel or washing liquid in modern motor vehicles and are known from practice as peripheral- or side-channel pumps. The impeller is typically fastened in a rotationally fixed manner to a shaft driven by an electric motor. During rotation of the impeller, circulation flows are produced in the vane chambers and a feed channel defined in the pump housing. The circulation flows deliver the fuel or the washing liquid from an inlet channel to an outlet channel. When the plural rings of vane chambers concentrically enclose one another, the feed pump may have several pressure stages or may supply various loads independently of one another. The impeller is usually produced by the injection molding or injection-compression molding process with tool molds corresponding to the impeller. The inclination of the guide vanes relative to the axis of rotation allows the feed pump to have a very high efficiency.
However, a problem with the known feed pump is that it is very costly to produce. For example, the rings of the vane chambers in each case require a complicated mold. During the demolding of the impeller from the mold, i.e., removal of the impeller from the mold, the impeller and the mold must be moved relative to one another in a specific manner. In addition, these relative movements must be followed precisely to avoid damage to the guide vanes.
The object of the present invention is to provide a feed pump having an impeller with guide vanes that are inclined by an angle with respect to the axis of rotation of the impeller such that the impeller may be manufactured with a high efficiency in a cost-effective manner.
The object is met according to an embodiment of the present invention by an impeller having rings of vane chambers delimited by guide vanes in which the guide vanes are inclined by an angle with respect to an axis of rotation of the impeller and the angle of the guide vanes is arranged to that it increases proportionally with increasing distance from the center of the impeller in the radial extent of the guide vanes. Furthermore, the angles of each of the guide vanes in a plurality of rings of the guide vanes arranged at one of the end faces has the same proportional relationship.
A suitable selection of the proportionality of the variation in the angle with respect to the distance of the guide vanes from the center of the impeller allows a common mold part to be used for producing a plurality of rings of the vane chambers. The use of a single mold part allows the impeller to be demolded without regard to relative movements. As a result, the feed pump according to the invention may be produced with a high efficiency and in a cost-effective manner. In addition, damage to the guide vanes caused by an incorrectly executed relative movement of the mold and the impeller during demolding is avoided. Furthermore, this design of the impeller allows a small number of mold parts to be used for production. The impeller may be produced with a total of two mold parts opposite one another. This produces an especially cost-effective tool use during the production of the impeller.
An especially high efficiency of the feed pump according to the invention, with ease of demolding of the impeller, may be produced in a simple manner if the angle of the guide vanes runs according to the formula             α      ⁡              (        r        )              =          arctan      ⁡              [                              r            *            tan            ⁢                          xe2x80x83                        ⁢                          (                              α                ⁡                                  [                                      r                    a                                    ]                                            )                                            r            a                          ]              ,
where r is any desired distance of an intended point of the guide vanes from the center of the impeller and xcex1(ra) is a desired angle at radius ra. The proportionality of the angular variation with increasing distance from the center of the impeller can be established in a simple manner by this design. Since the relative proportions given in the formula have a decisive effect on the forming circulation flow, flow losses are kept especially low. The flows in the feed channel are adapted to those in the vane chambers.
According to another advantageous development of the invention, the demolding of the impeller is further simplified if the angle xcex2 of the side of the guide vanes facing away from the intended direction of rotation at the distance r is slightly larger than the angle xcex1(r). This embodiment produces guide vanes that are thickened slightly with increasing distance from their nearest end face of the impeller. The mold part provided for the production of the vane chambers may therefore have tapering projections for the production of the vane chambers, so that the impeller can be removed in a simple manner after release from the mold part.
According to an embodiment of the invention, flow losses inside the feed channels or the vane chambers are kept especially low if the guide vanes have an angle xcex1(r) within the range including 10xc2x0 to 50xc2x0. The range of the angle xcex1(r), at an intended distance of the corresponding rings of the guide vanes from the center of the impeller may be established in a simple manner by selection of the angle xcex1(ra).
According to another advantageous development of the invention, the flow losses in the feed channel or the vane chambers are further reduced if the angle a(r) is within the range including 15xc2x0 and 38xc2x0.
The efficiency of the feed pump according to the invention is further increased if the vane chambers pass through the impeller and in each case have a guide vane at the end faces of the impeller, and if the guide vanes are oriented relative to the end faces so as to point in the intended direction of rotation of the impeller. This configuration allows axial flow through the feed pump and the impeller may therefore be of very compact construction in the radial direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.